@INPROCEEDINGS{ author={Sanchez, A. and Elvira, S. and de Castro, A. and Glez-de-Rivera, G. and Ribalda, R. and Garrido, J.}, journal={Industrial Electronics, 2009. IECON '09. 35th Annual Conference of IEEE}, title={Low cost indoor ultrasonic positioning implemented in FPGA}, year={2009}, month={nov.}, pages={2709 -2714}}